No abstract

Because human land use activities often result in increased fragmentation of aquatic and terrestrial habitats, a better understanding of the effects of fragmentation on the genetic heterogeneity of animal populations may be useful for effective management. We used eight microsatellites to examine the genetic structure of coastal cutthroat trout (Oncorhynchus clarki clarki) in Camp Creek, an isolated headwater stream in western Oregon. Our objectives were to determine if coastal cutthroat trout were genetically structured within streams and to assess the effects of natural and anthropogenic barriers on coastal cutthroat trout genetic variation. Fish sampling occurred at 10 locations, and allele frequencies differed significantly among all sampling sections. Dispersal barriers strongly influenced coastal cutthroat trout genetic structure and were associated with reduced genetic diversity and increased genetic differentiation. Results indicate that Camp Creek coastal cutthroat trout exist as many small, partially independent populations that are strongly affected by genetic drift. In headwater streams, barriers to movement can result in genetic and demographic isolation leading to reduced coastal cutthroat trout genetic diversity, and potentially compromising long‐term population persistence. When habitat fragmentation eliminates gene flow among small populations, similar results may occur in other species.

Forest ecosystems in the western United States evolved over many millennia in response to disturbances such as wildfires. Land use and management practices have altered these ecosystems, however, including fire regimes in some areas. Forest ecosystems are especially vulnerable to postfire management practices because such practices may influence forest dynamics and aquatic systems for decades to centuries. Thus, there is an increasing need to evaluate the effect of postfire treatments from the perspective of ecosystem recovery. We examined, via the published literature and our collective experience, the ecological effects of some common postfire treatments. Based on this examination, promising postfire restoration measures include retention of large trees, rehabilitation of firelines and roads, and, in some cases, planting of native species. The following practices are generally inconsistent with efforts to restore ecosystem functions after fire: seeding exotic species, livestock grazing, placement of physical structures in and near stream channels, ground-based postfire logging, removal of large trees, and road construction. Practices that adversely affect soil integrity, persistence or recovery of native species, riparian functions, or water quality generally impede ecological recovery after fire. Although research provides a basis for evaluating the efficacy of postfire treatments, there is a continuing need to increase our understanding of the effects of such treatments within the context of societal and ecological goals for forested public lands of the western United States.Gestión Post-Incendio en Terrenos Boscosos Públicos en el Oeste de E. U. A. Resumen: Los ecosistemas boscosos en el oeste de Estados Unidas evolucionaron a lo largo de muchos mile-nios en respuesta a perturbaciones tales como incendios naturales. Sin embargo, las prácticas de uso y gestión del suelo han alterado estos ecosistemas, incluyendo los regímenes de fuego en algunasáreas. Los ecosistemas boscosos son especialmente vulnerables a las prácticas de gestión post-incendio porque tales prácticas pueden influir en la dinámica del bosque y en los sistemas acuáticos de décadas hasta siglos. Por tanto, hay una mayor necesidad de evaluar el efecto de tratamientos post-incendio desde la perspectiva de la recuperación † † †email robert.beschta@oregonstate.edu ‡ ‡ ‡Current address: 958Postfire Management of Public Forests Beschta et al.del ecosistema. Examinamos, vía la literatura publicada y nuestra experiencia colectiva, los efectos ecológicos de algunos tratamientos post-incendio comunes. Con base en esa examinación, las medidas de restauración post-incendio prometedoras incluyen la retención deárboles grandes, la rehabilitación de guardarrayas y caminos y, en algunos casos, la siembra de especies nativas. Las siguientes generalmente son inconsistentes con los esfuerzos para restaurar funciones del ecosistema después del incendio: siembra de especies exóticas, pastoreo, colocación de estructuras físicas en y cerca del canal de arroyos, tala ...